You get a finisher t-shirt at almost every foot race. Run enough 5k's, 10k's, and marathons and those cloth badges of pride soon create a real space problem.
Of course, you could always throw them out, or give them to charity, but if it's in your nature to hold on to things to which you have an emotional
attachment, then going for a mention in the Guiness Book Of World Records for largest race t-shirt collection is the only option. Below are my important "first" t-shirts that
I'll hang on to forever. They're getting tired looking, because I actually wear them. A lot.